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Author Topic: A trial of assorted filters in Icom IC-706mkiiG  (Read 3328 times)

Posts: 349

« on: August 02, 2005, 03:51:29 AM »

HI!  I have bought two Icom IC-706s which I have
configured as mainly CW rigs on HF.  I have now
the {250 Hz, 350 Hz, 500 hz, 1.9 kHz} optional
filters as well as the default 2.4 kHz filter.

I tried {350 Hz/1900 Hz} for a while.  Sideband
sounded nice in the sharper 1900 Hz filter, but
it was too broad for CW.  The 350 Hz filter,
being the geometric mean of 250 Hz and 500 Hz
displayed a lot of selectivity, too much for
me to monitor the 7040 kHz hailing frequency
with the 350 Hz filter active.

I then installed {250 Hz/500 Hz}.  The 500 Hz
filter was perfect for monitoring the 7040 kHz
hailing frequency, I could hear stations which
were slightly off-frequency.  After establishing
contact, I move off and insert the 250 Hz filter
The 250 Hz filter really cuts down on QRM and QRN

Posts: 349

« Reply #1 on: August 07, 2005, 09:53:10 AM »

P.S. If you ever have to remove a filter, be really careful to pull the filter out straight.  Yes you can straighten the pins manually after you carelessly "yank" the old filter out, however do this too often and the pins will snap off due to metal fatigue(!)

Also please remember the thin clear plastic insulator that came with the optional filter is supplied for a purpose.  It should be installed  between the filter and the circuit board, where it prevents any untoward "short circuits".

Posts: 31

« Reply #2 on: August 08, 2005, 01:57:13 PM »

If you've got two 706 IIGs and four optional filters, you've got room to install all three of your CW filters AND your SSB filter. That's what I'd do.

Even if you operate SSB only occasionally, the 1.9 filter makes a big difference on this rig in that mode when there's lots of noise or QRM. With judicious use of the 1.9 filter and the passband offset knob, you can make readable phone copy out of pretty awful situations.

Don't judge the usefulness of the 1.9 filter, in advance of trying it, based on your experience with other rigs or other SSB filters. I've got an FT-897 with a 2.0 filter in it, and it's much less useful than my 706's 1.9. Both the 1.9 and 2.0 are Collins mechanical filters. I'd have expected the 2.0 filter to be almost as useful as the 1.9, since its passband is only about 100 Hz wider, but that's not the case. I love the 1.9 in the Icom but could easily live without the 2.0 in the Yaesu.

Posts: 349

« Reply #3 on: August 08, 2005, 04:20:31 PM »

I have two Icom IC-706mkiiGs (one N.I.B.) with the
filter pair {250,500} Hertz installed in each IC-706
Separately in boxes are two pairs of {350,1900} Hertz
filters.  For the test I installed {350,1900} Hertz
filters instead of the normal {250,500} Hertz filters.
I am not a sideband addict, and after owning one of
the IC-706s since Fall of 2003, I actually spoke on
SSB a week ago the word "test" and watched the ALC
meter bounce.

I do not foresee swapping the crystal filters again.
Removing filters can damage the pins on the bottoms,
which can be straightened, but you can only do this
for _so_ long, before the pins snap.
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